Construct Concrete Bathtub I Am Trying To Construct Concrete Walls In A Rather Unique Way. Will My Plan Work?

I am trying to construct concrete walls in a rather unique way. Will my plan work? - construct concrete bathtub

I think the motion of two drywall about an inch and parallel to the ends of seal and the casting of the concrete between the panels of plaster to create a concrete wall. Will it work? Problems, concerns?